Proteins with covalently bound heme and tetrapyrrole (bile pigment) prosthetic groups are a class of brilliantly clored, intensely fluorescent compounds found in all organisms. They have important roles in electron transport, photochemical reactions, and metabolic processes. The objectives of this investigation are to establish the structure and absolute stereochemistry of each pigement-peptide moiety, to establish the detailed biosynthetic mechanism by which each pigment-protein combination is formed, and to develop synthetic methods so that these molecules and their analogues will be available for structure-activity studies.